Remotely pumped free-space optical (FSO) communication terminals

ABSTRACT

This invention pertains to the field of free-space optical (FSO) communications, and specifically to the realization of functional FSO optical transceiver terminals located at remote electrically unpowered locations within a communications network. A remote unpowered FSO terminal located at a far-end location receives necessary optical power from a powered base station location (near-end) required for all optical amplification functions necessary for NRZ or RZ format signals within the spectral range of 900 nm to 1480 nm as well as an Ultra Short Pulsed Laser (USPL) centered at 1560 nm at the far-end location. A transmitting node identified as the near-end transmits an optical signal identified as a pump signal to a remote location classified as the far-end node over a free space medium, such as the atmosphere, where the far-end node location does not have available electrical power for operation of electro-optic components required for transmission and retransmission functions.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/472,423 filed on Mar. 16, 2017, titled REMOTELYPUMPED FREE-SPACE OPTICAL (FSO) COMMUNICATION TERMINALS and U.S.Non-Provisional patent application Ser. No. 15/842,619 filed on Dec. 14,2017, titled WAVELENGTH DIVISION MULTIPLEXING PER PULSE FROM ULTRA SHORTPULSED LASERS USED IN FREE SPACE AND FIBER OPTICAL COMMUNICATION SYSTEMSand to U.S. Non-Provisional patent application Ser. No. 15/582,693 filedon Apr. 30, 2017, titled USPL-FSO LASERCOM POINT-TO-POINT ANDPOINT-TO-MULTIPOINT OPTICAL WIRELESS COMMUNICATIONS and to U.S.Provisional Patent Application Ser. No. 62/627,563 filed on Feb. 7,2018, titled METHOD AND APPARATUS FOR ULTRA-SHORT PULSED LASERCOMMUNICATION THROUGH A LOSSY MEDIUM the contents which are all herebyincorporated by reference herein.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION Backgroundof the Invention 1. Field of the Invention

This invention relates to free-space optical (FSO) laser communicationsnetworks, including ultra-short pulse laser (USPL) communications, andin particular, but not exclusively, to optical regeneration andretransmission of communications signals received at remotecommunications transceiver sites that do not have available sources ofelectrical power. Rather, such transceiver sites are energized by thetransmission of optical power to them from another transceiver site inthe network that does have an electrical power source. Novel use ofoptical pumping amplification of received data is described without theneed for electrical power at such transceiver sites that lack electricalpower. Such FSO communication networks shall operate uni-directionallyor bi-directionally within any spectral band.

2. Description of Related Art

Terrestrial and submarine optical communication networks have dominatedthe telecommunications industry in supplying high capacity informationhighways for private and commercial needs. In such designs, optical datasignals are transported and guided within optical transmission fiber asa propagating medium.

As optical signals are transported within an optical fiber, each datastream experiences a logarithmic decrease in optical power level as afunction of distance.

To compensate for optical transmission loss, attenuation, through fiber,optical amplification techniques are installed into repeater housings atpredetermined positions within a network. Such repeaters house necessaryelectro-optical and network management functions required foramplification functions, along with provisions for electrical power.

Accordingly, these functions within a repeater require electrical power,and limit the reach, cost and overall versatility of network deployment,especially in certain urban and rural regions.

Growth in demand for telecommunication services, from both the privateas well as commercial sectors has placed an unprecedented strain uponcurrent telecommunications networks. Without alternate network systemtechnologies and delivery topologies, overall effective network speedwill be reduced and frequent bottlenecks within networks will becomemore commonplace in the very near future.

Free-space optical communications networks provide a natural alternativeto fiber based, microwave links, wire, or cable system applications,where feasible. These networks are transparent to current as well asfuture network architectures in that they share common technologicalplatforms with fiber optic transmission systems, the backbone of thepresent day telecommunication systems¹.

Free-space optical (FSO) communication networks share common fiber-opticcomponents to terrestrial and submarine systems, in that identical O-,C- and L-band lasers, and receivers can be utilized for bothapplications. The only exception for FSO data link systems is that themedium of propagation is the atmosphere.

Utilizing current state-of-the art USPLs and other fiber-optic lasersand components, FSO data links can be fully integrated into currentshort- and long-haul high-speed optical networks. Utilizing current 1550nm technology platforms FSO data links can fully attain current systemarchitectures, additionally the systems can be completely scaled tohigher data rates and configurations.

Additionally, because of the operating wavelength of the system, issuesrelated to eye safety are minimized. Furthermore, no special precautionsor permits need to be issued for operating a free-space data linkrelated to territorial right-of-ways, expenses related to plowing andtrenching of fixed cabled system can be waved as well.

Current laser communications terminals or FSO laser communicationsterminals require electrical power to achieve electro-optic regenerationof received signals to operate as effective network elements.

Incoming optical signals received at remote transceiver locations,require optical-electrical-optical conversion processes to occur inoperation of FSO links. As such an external power source, typicallyelectrical is required to implement this technique. Thus in certainenvironments where external power sources are not available, thisapproach is not feasible for utilization of an FSO type data-link.

Optical FSO tranceivers having electrically powered provisions havevarious limiting issues, wherein the cost and complexity is a majorfactor. Another drawback to currently used FSO transceivers is in thedata-rate specific designs where operation is typically limited to aspecific operating line rate. Operationally, such systems requireextraordinary manufacturing hardware and assembly complexity.

However presently used or considered approaches rely upon directcurrent, batteries, solar cell power technologies as well as otherconsiderations. As such, these alternatives are complex, costly, requiremaintenance of batteries, pose a health and fire risk along withpotential reliability of operation, and added costs in production andassembly.

There is thus a need in the art for an effective way to implement apassive technique to realize remote optical amplification, regenerationand retransmission capabilities while reducing complexity andmaintaining network reliability for FSO transport traffic.

SUMMARY OF THE INVENTION

In this disclosure, an optical pump source in a transceiver located at abase-station (near-end) location is transmitted over the air to anunpowered remote (far-end) transceiver location. At the far-endtransceiver, received pump power is used to amplify data-signals presentat the far-end location. Commonly used procedures, components andpractices used in optical amplification technology are employed. Inpractice, optical pump signals transmitted from a near-end transceiverlocation via free-space are received at a far-end transceiver location.

The pump signal received at a remote transceiver location providesnecessary optical pump power for use in the optical amplificationprocess and used to amplify low-level signals present at the far-endtransceiver location for propagation back to the near-end location orother nodes present within the network. In this manner, bi-directionallinks are established, without the need or requirement for electricalpower at remote (far-end) locations.

In a similar manner, available pump power at a far-end location canextend optical transport to directions other than direct lines of sight.Since FSO technology is directed along a single line-of-sight-path,secondary or intermediate base-stations can be remotely poweredappropriately as required for links covering such non-linear paths. Insuch situations an intermediate base-station located at an optimumposition allow for redirection to the far-end, non-line-of-sightpositions.

Functionally a FSO data link consists of a telescope for transmittingfrom a near-end node an optical signal toward a second telescope locatedat a far-end. In principal, the far-end receive telescope collectsincoming signals from the near-end, where data transmitted can be withinthe optical O-, C, and L-bands or other bands. Incoming light collectedat the far-end transceiver, detected by appropriate photo-detectorhardware required for data recovery and retransmitted onto the network.FSO transceivers operate bi-directionality, sending informationsimultaneously within the network.

At the far-end site, available local pump power can re-amplify incomingdata signals with erbium-doped and or erbium/erbium doped fibersegments. In this capacity, an amplified signal is couple to anothertransmitting terminal element for transmission to another network nodelocation.

Modern day fiber based optical communication networks utilize alloptical repeaters to amplify data streams transported within glassfibers after signals have experienced attenuation in optical powerlevels. Such repeaters amplify attenuated signals after span propagationthrough the glass medium to a level to offset optical span losses. Torealize optical amplification local electrical power is required tooperate necessary optical pump lasers present within each amplifierstage. Such amplifiers are fiber based and incorporate transitionelements such as erbium (Er-63) and or ytterbium (Yb-70) to produce amedium capable of amplification within the 1520 to 1650 nm opticaltransmission windows. Although mentioned, the disclosure is not limitedto optical amplification elements of erbium and ytterbium, but may alsoinclude other chemical constituents such as praseodymium (Pr-59) andothers in like within the Lanthanide and Actinides series of elementsused for optical amplification within the optical window about 1300 nm.

To produce an amplifying glass medium, pump lasers are used inconjunction with the amplifying glass medium to optically invert themedium in the presence of incoming attenuated data signals, therebyachieving optical amplification. Typically, pump lasers used in opticalamplifiers operate at 980, 1450 and 1480 nm, and are directly coupledinto the glass transmission medium using standard fiber fusiontechniques and components. As such optical amplification of low powerincoming optical data signals can be as high as +30 dBm and higher. Insuch cases pump lasers are required and available to produce requiredpower levels to invert the glass medium in order to achieve requiredoutput levels. As such modern day pump lasers can supply optical pumplevels in excess of 300 Watts of optical pump power @ 1480 nm.

By way of comparison, one optical channel passing through a +30 dBmamplifier would have +30 dBm of optical power associated with this onechannel. Having four propagating channels passing through such anamplifier each output channel would have +24 dBm of optical power withthe aggregate power level equal to +30 dBm.

Optical amplification technology, similar to technology used interrestrial and submarine application is employed for FSO link operationin order to offset optical loses incurred due to atmospheric andtransmission losses between various node locations. As such, FSOterminals need to be provisioned with electrical power in order tofunction as independent optical node terminals.

This disclosure illustrates a means of providing optical amplificationfunctionality, (passively) without the need or requirement of supplyinglocal electrical power to far-end or intermediate terminal locationswithin a FSO data link, or network topology architecture and classifiedas a passive-FSO (p-FSO) optical terminal.

It is an advantage of this invention that problems of the prior art, inparticular insufficient power and insufficient bandwidth, are overcome.In overcoming these and other problems, the invention (among otherthings) provides techniques for design, realization of FSO networks andprovides flexibility in positioning optical nodes within a networkwithout the need for provisioning nodes with electrical power foroperation.

This disclosure describes an approach to address issues related toproviding a means to realize optical amplification, regeneration andretransmission capabilities to conventional remote FSO terminal withoutthe need or requirement of local powering.

The approach presented in this disclosure is to use operationally p-FSOterminal designs along with a data-rate agnostic configuration at aremote terminal location. Having unpowered repeater type FSO terminalsprovide unique means to extend network service using unpowered remoteterminal elements.

Having agnostic, data-rate insensitive FSO terminals provides theability of the p-FSO system to adapt immediately to various changes dataline rates without having the need to perform equipment changeover,thereby saving time and costs.

The p-FSO terminal segments function by transporting from a near-endterminal node, data signals as well as optical pump power required atthe far-end location to facilitate optical amplification at the far-end.At the far-end, data signals present can undergo optical amplificationenabled from optical pump power supplied from the powered near-end orother similar nodes.

The p-FSO optical link established may include multiple pump sourcessupplied from various network node locations. Such coupling has thepotential to increase reliability and/or efficiency of the opticalcommunications system, as well as to extend network reach.

In this disclosure, a dedicated optical pump source, including adedicated USPL pump source, located at a near-end location istransmitted to an unpowered far-end location, where the received pumppower is coupled into segments of erbium-doped and orerbium/ytterbium-doped fibers providing optical amplification. Suchoptical pumping schemes are commonly used within the optical networkingindustry as a means to extend the reach of data signals, especiallywithin, but not limited to, the O-, C- and L-bands. Light frequenciestransmitted by Ultra Short Pulsed Lasers (USPLs) might be converted uponreception with known frequency-conversion techniques so that theincoming light is changed to the suitable pump frequencies.

The pump signal received and supplied to a far-end node locationprovides necessary optical pump power for use in the opticalamplification process. Received optical pump power at the far-endlocation provides the means to amplify low-level signals present at thefar-end location for propagation back to the near-end transceiverlocation or other transceivers present within the network. In thismanner, bi-directional links are established, without the need orrequirement for electrical power at far-end or remote locations.

In a similar manner, available pump power at a far-end location canextend optical transport to directions other than direct lines of sight.Since FSO technology is directed along a single line-of-sight-path,secondary or intermediate base-stations can be remotely poweredappropriately as required for links covering such non-linear paths. Insuch situations an intermediate base-station located at an optimumposition allow for redirection to the far-end, of non-line-of-sightpositions, providing the means to adapt to network geographicalconditions.

To realize capabilities presented within this disclosure, a high-poweredlaser pump source is employed at one network location, where power andnetwork assets are available at the near-end.

Unpowered-Repeater FSO, p-FSO transceivers operating without activeelectro-optic elements at remote locations within an optical network,provide a low cost, secure and efficient alternate means of extendingnetwork reach without compromising functionality.

To realize remote pump capabilities a high-power pump source transmitsthrough a large aperture telescope with a low divergence angle towardthe remote site of interest. In this manner, the near-end base-stationlink provides the source of pump power required at the remote location.Such pump lasers can be Continuous Wave Lasers (CW) or Pulsed Wave Laser(PW), and can operate in any of the major atmospheric and ortelecommunication transmission windows.

Large aperture telescopes are commonly available with the necessaryoptical quality to provide a low-divergence angle of transmission tominimize optical spreading at the remote location, thereby enhancing theoverall coupling efficiency between the two distant links.

The receive and transmitting telescopes may be any typical telescopetypes and or newer parabolic off axis telescopes. In some cased it maybe beneficial to not have a secondary mirror (the small mirror in frontof the big one) as in the case of the Ritchey-Chretien telescope designwhere the secondary mirror could produce near-field diffraction affects,which would distort the pulse. A workaround to this problem is anoff-axis telescope design, which requires an off-axis parabolic mirroras the primary (large) mirror.

Such telescopes are provisioned as required to launch and receiveoptical signals using bulk optics or fiber coupling elements.

Although bi-directional point-to-point links are described within thisdisclosure, the concept and intent may be extended; multi-point,multi-hop, star type network architectures and topologies, and one-waypasses.

The applications described within this disclosure identifies terrestrialbased systems but shall also find value in satellite-FSO communicationssystems in similar topologies as well as in undersea submarine-FSOcommunication links.

In all cases; terrestrial-FSO, satellite-FSO, and submarine-FSOtranceivers provide, the ability to provide a passive solution withoutthe need or necessity of added weight and costs will provide a novelmeans for reducing costs, weight, network flexibility and operationalreliability.

In one embodiment, a data source signal within the optical C-Band and asuitable pump signal can co-propagate from a base-station, near-endtelescope launch site to a remote location. At the remote location,far-end, C-Band and pump signals couple into a telescope at the receivesite and routed into an optical amplifier stage using either bulkoptical components and or fiber-coupled components. Standard opticalfiber amplifier technologies along with suitable optical elements areused within this disclosure.

Optical amplification at the far-end transceiver is performed in amanner identical to standard conventional techniques without however therequirement of electrical power to be supplied for pump operation, wherethe optical data link has supplied the necessary optical pump powernecessary for optical amplification functions.

The manner by which remote optical pumping is performed althoughmentioned as standard means may be extended to other types of opticalpumping schemes such as high-powered pulsed laser systems as well asRaman pumping schemes.

Having available pump power at a remote location can provide extendedcapabilities for providing the means for a return link to be establishedwith the base-station east-end location, where a low level signalpresent at the remote station is transported as required.

The pump power laser beam and the communications data signal can be onseparate lasers or the same laser. For these to be on separate signalsthere may be a difference in power levels and so best practices must beused to keep them separate. For example, different laser wavelengthsmight be used for the different signals and different detectors would beused for these wavelengths. Additionally, there may be differentplacement of the respective detectors relative to the transmittingoptics. The transmitting optics may be separate physical systems or thetwo signals might be co-propagated in a single transmitting element. Theseparate detectors might be ‘stacked’ whereby one of the signals mightpass transparently through one detector and be received ‘behind’ theother. Another configuration might allow for the two signals to belaunched with two separate divergences such that the POWER signal ismore broadly spread out thereby allowing a detector configurationwhereby the communications detector is in the center of a much largerpump power signal rectifier that surrounds (in a much larger concentricpattern) the COMMUNICATIONS detector. Another embodiment might be thatthe receive telescope is designed (through surface treatments possiblyincluding the inclusion of mirrors that focus only certain wavelengthsto certain detectors or rectifiers etc.).

For the pump power and communications data signals to be one and thesame, one configuration might be to data modulate a lower power signal(for example, coming directly from the oscillator) that is thenmodulated and then sent to the amplifier prior launching the signal.This approach will preserve and extend data modulator life. For maximumreceived power, a data modulation scheme can be chosen that uses all ofthe amplifier power available over a certain amount of time. Forexample, an On-off Key (OOK) data modulation scheme can be used in thisdesign but in some cases this may lead to less efficient amplifieroperation as the amplifier is receiving random series of pulses or ‘nopulses’ leading to uneven peak pulse power levels in the launchedpulses. By contrast, a pulse position modulation (PPM) scheme might bepreferable as the amplifier will always receive a pulse in a certaintime slot, potentially leading to more even peak pulse powers launchedand less stress on the optical detector system. Regardless, whencombining both pump power and communications data into one signal, onesimple receiver configuration might be to put an optical attenuator inline after the receive optics that redirects and rectifies all extrapower received over a certain threshold.

Any received pump power over and above that necessary to operate theremote FSOC transceiver can be used for any other local system requiringpower. This concept is straightforward but can be embodied in variousconfigurations, specifically, bussing approaches whereby any extra powerfrom the remote source that is not needed to operate the FSOCtransceiver, can be routed to any other local (to the remote FSOCtransceiver receiving the pump power signal) system that may need powerto operate as well.

This disclosure contemplates a transmitting optical telescope includingobjective optics, to transmit various wavelengths of light within anyoptical band used for state-of-the-art continuous wave free spaceoptical communications systems or expected to be forthcoming usingultrashort pulse lasers and their characteristic broadband signals whichcan span many octaves of light frequencies below or above the O-, C- andL-optical bands. Supporting this is the fact that ultrashort pulselasers (USPLs) have now been demonstrated in FSOC systems by Attochron,LLC and as such represent potentially extremely broadband light sourcesfor FSOC that extend the range of FSOC signals far beyond anything thathas come before from the continuous wave (CW) laser state-of-the-art.USPL sources now exist from many established laser makers that emitanything from ultraviolet wavelengths to far into the infrared (4microns an beyond). Separately, newer supercontinuum (SC) USPLs provideextreme broadband light sources where a single SC USPL will emit wellbelow the O-band and well above the L-band (spanning the O-, E-, S-, C-and L-bands in a single laser) for a USPL FSOC system for example seehttps://www.rp-photonics.com/supercontinuum_generation.html.

Because the USPL can emit such broadband signals—potentially spanningoctaves of light frequencies—it is possible to use some of the lightfrequencies as pump frequencies either by ‘slicing’ the necessaryfrequencies out of the complete USPL signal and/or leverage the knowntechniques of frequency-conversion (i.e. second harmonic generation,third harmonic generation; frequency doubling, tripling, etc.) to ‘up’or ‘down’ convert the received light frequencies to the required pumpfrequencies.

The system may include pointing and tracking systems as well as adaptiveoptics systems for purposes of optimizing the system's overallavailability as well as the efficiency of power transfer. Unlike FSOcommunications-only systems, where enough power on target to ensuresuitable telecommunications processes are occurring, the objective ofthis technology is to also get the maximum total power on target (to thereceiver/rectifier/etc.) for the purposes of supplying the power thereceiving system needs to operate. So anything that can be done todirect and focus/collimate the transmitted optical power to thereceiver, rectifying element, etc. should be considered. Pointing andtracking (P&T) allows the system to acquire & then track the target,i.e. the launch optics (by the receiving optics) or receiver optics (bythe launch optics) should either the transmitting element and/or thereceiving element be in any kind of movement). Adaptive optics (AO) is ageneral term referring to real-time adjustments of certain opticalelements in the FSO and/or FSOC platform. AO can augment the P&Tcapability by (for example) literally focusing the lens surface (in arefractive system) and/or perform other functions automaticallyincluding ‘active divergence’ (the real-time collimation of the emittingand or receiving optics), etc.

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims.

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawingswhich are given by way of illustration only, and thus do not limit thepresent invention and wherein:

FIG. 1 is a block diagram of fully functional FSO data link with networkconnectivity, according to the invention; where the FSO link as shownconsists of two individual send (transmit) and receive optical elements.

FIG. 2 is a functional block diagram of a generic FSO Transceiver,providing bi-directional capabilities, according to the invention;

FIG. 3 is a functional front-end view of a generic FSO Transceiver,illustrating bi-directional capabilities, according to the invention;

FIG. 4 is a functional block diagram of a generic optical amplifiermodule along with optical components required to perform opticalamplification capabilities, according to the invention;

FIG. 5 is a functional block diagram of a Near-end FSO terminal forlaunching optical pump power launch to a far-end, unpowered FSO terminalat a remote location to facilitate optical amplification at a remoteunpowered far-end location, according to the invention;

FIG. 6 is a functional block diagram of a transmit FSO transceiver forlaunching both optical pump power for remote usage along with in-banddata signals, to a far-end, unpowered remote location to facilitateoptical amplification at a remote unpowered far-end location, accordingto the invention;

FIG. 7 is a functional diagram of a far-end unpowered FSO transceiverdescribing reception and separation of received pump and data signals,according to the invention;

FIG. 8 is a functional diagram of a far-end unpowered FSO terminalillustrating amplification of local optical data signal and deliveredoptical pump power as provided from the transmit end location, accordingto this invention;

DETAILED DESCRIPTION OF THE DRAWINGS

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims.

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations.

FIG. 1 describes essential elements incorporated within a FSO data-link,where element 10 represents a network data signal operating at a nominaldata rate at a wavelength of 1550 nm. Although identified as a 1550 nmsource signal element 10 can represent any typical optical sourceincluding an USPL source within the O-, C- and L-bands or other selectedbands, and can be directly coupled to transmitting element 102 throughthe use of fiber optic cabling or free-space coupled as identified byelement 101. Element 102 represents the launch transceiver's opticaltelescope for signal transport over free-space where the amount ofoptical divergence can be controlled through proper adjustment ofoptical elements within element 102. Element 103 represented thelaunched or transported optical signal from element 102. Element 104represents the optical signal presented to the far-end receivetransceiver, after propagating through the optical data-link span, wheregeometrical spreading losses as well as known atmospheric effectsattenuate the effective optical power level at the remote transceiver'stelescope receive aperture identified as element 105. Elements 103 and106 are effective optical power levels after signals have beenattenuated through optical elements 102 and 105 respectively. Telescopeinsertion losses can be minimized through proper design and aperturearrangements. Elements 20, the far-end laser launch source, 202 far-endtransceiver's telescope launch optics along with element near-endtransceiver's telescope 205 constitute a second optical transmit path,203 and 204, from the far-end to the near-end and provide bi-directionallink functionality. Element 301 is the effective optical power levelafter signal 104 has been attenuated through transceiver's telescopeelement 205. At each location, near- and far-end electrical power isrequired in some form for link functionality, to provide the necessaryoptical power level to overcome atmospheric and geometrical, as well asoptical insertion losses for link operation. In many cases, linkoperation is dependent upon the amount of optical power available toprovide “link-closure” or the ability of the receive location to detectincoming data-signals. In each case, link margin provides an indicationof the amount of power available to overcome expected link losses.

FIG. 2 identifies the main features for an electrically powered FSOtransceiver, wherein elements 102 represent a plurality of possibletransmitting optical telescope elements used for launch data signalsfrom source 10. Within the figure elements, 101 can represent opticalfiber interconnections or bulk free-space optical coupling to telescopetransmitting elements 102. Although source 10 is identified as a singlesource this element can be replaced by a 1×N (where N is an integergreater than 1) optical splitter, wherein an incoming optical signal isdivided as required to a corresponding number of transmitting elementsas described by element 102. In another embodiment element 10 can bereplaced by multiple optical sources and coupled to various opticalelements as required and depicted by element 102, and launched intofree-space as depicted by element 103. Element 204 represents afree-space optical signal propagating inbound into receive element 205.Element 205 may consist of any appropriate optical telescope of eitherthe reflective or refractive type, and provisioned to couple directlyinto an optical receiver directly or into other optical elementsproviding necessary functionality, such as an optical circulator,optical de-multiplexer or the like, using either bulk optics or fibercoupled as required can be incorporated, where these functionalcapabilities are identified by element 207.

FIG. 3 provides a front-end illustration of one possible configurationof a FSO optical transceiver; where for illustrative purposes fourtransmitting elements identified as 102 is shown. For each aperture,single-mode or multi-mode optical fiber can be utilized forinterconnection to each element or if required bulk, free-space opticalassemblies. Element 205 represents the receive aperture for thisparticular transceiver element.

FIG. 4 presents essential basic elements used in standard opticalamplifier designs, where actively doped optical fiber represented byelement 700 is optically pumped by an optical pump source identified byelement 704 that is activated by electrical power source 701 inconjunction with a low power level data-signal identified by element 703that is activated by electrical power source 702. The optical outputsfrom Elements 703 and 704 are coupled into element 700 through the useof a suitable optical coupler identified by element 705. In all cases,elements 703, 704 and 705 may incorporate either single or multi-modeoptical fiber designs. Element 706 provides the optical data signal asamplified through element 700.

In another embodiment, the optical amplifier design illustrated in FIG.4 may utilize a multi-mode optical amplifier design previously cited inU.S. Pat. No. 6,348,684 titled RECEIVING SYSTEM FOR FREE SPACE OPTICALCOMMUNICATIONS BY g, Nykolak et al. granted Feb. 19, 2002, where opticalinputs into the amplifier stage are based upon a multi-mode opticalfiber technology.

FIG. 5 illustrates a single function design for the near-end(transceiver segment), where only a pump signal is illustrated andtransmitted to far-end transceiver Elements 30, 302, and 109 representthe pump source, WDM coupler, and propagating pump signal from thelaunch telescope 108 element respectively. Element 108 is identified asa suitable optical transmit telescope aperture.

FIG. 6 illustrates the addition of a data channel for free-spacepropagation to a far-end transceiver in conjunction with a dedicatedpump source for use at the far-end only. The optical data channel,identified by element 10 in FIG. 6 may be a conditioned opticallyamplified signal previously amplified by separate means at the near-end,for efficient propagation to the far-end. As such, ancillary opticalamplification functions for element 10 are provided separately.Identified by element 109 of FIG. 6 both the signal channel, 101 andwell as the pump source identified by element 301 may co-propagate alongthe same optical paths 107 and 109 before entering and after leavingtelescope 108 or may incorporate separate optical launch optics andpropagate along adjacent paths (not shown).

FIG. 7 illustrates the basic design features accompanied as realized ata far-end location, where an incoming signal 110, containing both pumpsource and data channel, identified as an egress signal 110 to a receiveelement identified as telescope 108. Signal separation is accomplishedby element 120, an optical de-multiplexer separating received opticalelement 111 into pump and data channels as identified by elements 130and 140 respectively. In all cases described multi-mode optical fiberinterconnections are used to providing efficient coupling. As a resultof this operation a resident and available pump source has been providedto the far-end location for required system use. The data channel 140can be provisioned for further transport to other network transceiversor to another FSO type of telescope element for re-transmission toanother transceiver, location.

FIG. 8 presents details related to routing of laser pump and datachannels at the far-end transceiver location along with amplification ofadditional network capacity at a remote unpowered FSO transceiver. InFIG. 8 element 110 represents an incoming optical signal containing bothremote amplifier pump power identified by element 130 as well astransported data capacity identified by element 140. Telescope Element108 captures incoming element 110 and couples the received opticalstream into an optical de-mulplixer identified by element 120. Element120 separates pump power identified by element 130 from the data streamidentified by element 140. Element 140 is routed to available networkhardware for interconnection into other transceiver network elements.Element 130 couples into element 141, that combines received pumpelement 130 with data capacity located at the far end identified byelement 139. The coupled output from element 141 is coupled by way ofoptical fiber element 152 to an optical amplifier element as identifiedby element 30 shown in FIG. 8. In so doing local data traffic, asidentified by element 139, is remotely pumped and provisioned forfurther transport to additional network elements in fiber or FSOtransport networks.

What is claimed is:
 1. A free-space optical (FSO) communications networkincluding an electrically powered near-end transceiver and one or moreremote (far-end) transceiver(s), the near-end transceiver having one ormore transmit apertures configured to transmit, via FSO laser beam(s),both data signals and optical pump power effective to activate the oneor more remote (far-end) transceiver(s) that do not have local source(s)of electrical power, wherein the near-end transceiver includes one ormore transmitting telescope(s) that are used to transmit optical pumppower levels along with co-propagating data signals to remotetelescope(s) associated with one or more of the remote transceiver(s)that are designed to couple received optical pump power to opticalamplifier(s) within the remote transceiver(s) to amplify incoming datasignals so that the remote transceiver(s) have the ability to provide alevel of optical amplification for NRZ, RZ or other data transportmodulation formats without.
 2. The free-space optical (FSO)communications network in claim 1, wherein the optical pump powerreceived by the remote transceiver(s) can be split into two parts sothat one part can be used to optically amplify the incoming optical datasignal and the other part can be converted by solar cells to produceelectrical power to fully energize the remote transceiver(s).
 3. Thefree-space optical (FSO) communications network in claim 1, havingtransceivers equipped with objective optics to transmit variouswavelengths of light within any optical band used for continuous wavefree space optical communications systems using ultrashort pulse lasers(USPL).
 4. The free-space optical (FSO) communications network in claim1, wherein the transceiver telescope(s) comprise a configurationselected from the group consisting of Schmidt-Cassegrain,Ritchey-Chretien, Dioptric (refracting), Catoptric (reflecting),Catadioptric, and parabolic off axis telescopes.
 5. The free-spaceoptical (FSO) communications network in claim 1, wherein the opticalamplifier(s) in the remote transceiver(s) comprise an erbium doped fiberamplifier or an erbium-ytterbium doped fiber amplifier.
 6. Thefree-space optical (FSO) communications network in claim 1, wherein thetelescope(s) associated with one or more of the remote transceiver(s)have a sufficiently large optical aperture and, if required, pointingand tracking as well as adaptive optics capability for optimizing thenetwork's overall efficiency of optical data and optical power transferand, thereby, the network's overall availability during inclementatmospheric conditions.
 7. The free-space optical (FSO) communicationsnetwork in claim 1, wherein the remote transceiver(s) include a mediumto amplify the received data signals along with received pump power andrelay the optically amplified data signals to another transceiver or asequence of transceivers, thereby providing either a single-hop or amulti-hop transmission path for the optically amplified data.
 8. Thefree-space optical (FSO) communications network in claim 1, wherein someor all of the transceivers are capable of bi-directional operation. 9.The free-space optical (FSO) communications network in claim 1, whereinsome or all of the transceiver(s) include multiple lasers for datatransmission and multiple lasers for producing pump laser beams.
 10. Thefree-space optical (FSO) communications network in claim 1 that isoptimized for terrestrial applications, wherein various optical datasignals may be coupled into terrestrially based fiber opticcommunication systems.
 11. The free-space optical (FSO) communicationsnetwork in claim 1 that is optimized for submarine applications.
 12. Thefree-space optical (FSO) communications network in claim 1 that isoptimized for satellite applications.
 13. The free-space optical (FSO)communications network in claim 1, wherein the optical amplifier(s)within the remote transceiver(s) comprise a multi-mode optical amplifierthat obtains optical pump power for amplification from the electricallypowered near-end transceiver.
 14. The free-space optical (FSO)communications network in claim 1, wherein the optical amplifier(s)within the remote transceiver(s) comprise an erbium amplifier designsuch that the received power is coupled into a 1480/1550 nm coupler.